Inhibiting explosions in coal mines and the like

ABSTRACT

This application discloses inhibiting of explosions in coal mines and the like by broadcasting an inert material in the mine in the form of finely divided shells of bivalves.

OR 345959317 :SR

UIlllCfl DlaltfS l'aliilll [72] Inventor Samuel M. Bell Windsor Road. Pittsburgh, Pa. 15215 [21] Appl. No. 12,847 [22] Filed Feb. 19, 1970 [45] Patented July 27, 1971 [S4] INHIBITING EXPLOSlONS IN COAL MINES AND THE LIKE 7 Claims, No Drawings [52] U.S.Cl l69/2R [5 I] Int. Cl A62c 3/00 [50] Field ofSearch 169/2 I 56] References Cited UNITED STATES PATENTS 1,568,281 1/1926 Jones 169/2 6/1932 l0/l941 8/l967 l/l969 Gray et al. 169/2 X Lambetal..... 169/2 Diamanti 1. 169/2 X Heavilon et al 169/2 Jamison 169/2 Primary Examiner-Lloyd L. King Attorney-Buell, Blenko & Ziesenheim bivalves.

INHIBITING EXPLOSIONS 1N cont. MINES snows LIKE mines and the like by introduction of inert materialinto the mines. More particularly it relates to use of finely divided bivalve shell material as an inert material, which willinhibit explosions and also improve health and working conditions in mines. v

Removal of carboniferous deposits from the earth in the form of coal or lignite is widespread and occurs in many different parts of the world. Removal may be by strip mining' or by underground, or deep, mining. Underground mining nor-' mally employs a series of parallel entries or haulageways extransversely extending crosscuts at intervals.

The steps of blasting, drilling, and cutting, and also operation of continuous mining machines produce substantial quantities of coat dust, rock dust, and fumes. The terms coal" and tending from a shaft or portal to the working face and having coal dust" here are intended to be comprehensive of carworking face and an exhaust from the working face'to the atmosphere. I i

As .has been noted above,the various mining'operations produce fine coal dust in varying amounts. The moving airstream employed for ventilation tends to carry the dust throughout the mine, and hat dust is sometimes known as float coal". Finely divided coal dust tends to be .unstable because of the high ratio of surface area to volume, and may lead to dust explosions in the confined places. Also, a relatively minor explosion in one part of the mine may be propagated throughout the mine by-the presence of fine coal dust.

abundantsupply. Old shells, in the order of 5,000 years'old,

have proven to be highly satisfactory. I wash the shells to It has long been customary, both as a matter of' good mining practice and because of legal requirements, to inhibit and suppress mine explosions by providing an adequate quantity of fresh air to remove combustible gases. Additionally the coal dust has been diluted andintermingled with an inert rock dust material to prevent propagation of an explosion in :the'coal dust. While various rock dusts are acceptable, the most commonly used appears to be finely divided limestone which is distributed throughout the mine including the airways carrying miners. Recent studies increasingly evidence that the silica isinjurious to the health of the miners. As a result mining opera: tions are now rock dusted with limestone having a maximum silica content of 5 percent, and preferably lower. Obtaining such material, particularly of lower silica content, is often inconvenient and/or expensive, however.

I have invented new methods for inhibiting explosions in coal mines and the like.'l employ a common and readily obtainable material and by appropriatetreatrnent of it attain a far superior result than any previously attainable while maintaining a price which is comparable with prior materials.

Moreover, the danger to miners by reason of silica inhalation resulting from rock dusting is virtually eliminated. l employ as a starting material, the discarded shells of bivalves which are found in profuse deposits in ocean areas and are in p 7s remove loose silica, such as sand, from them. Thereafter the I 'shells are ground to finelydivided form, introduced into the I This invention relates to inhibition of explosions in coal 5 mine and broadcast in the mine including onto the walls of the mine and into the airstream. As used here, the term walls ineludes the horizontal walls (floor and ceiling) as well as the vertical walls. The shell material may be broadcast by shovel,

by conventional machinery, or by injection into a moving layers and be readily reduced to finely divided form. The density of the shell'material more nearly approaches the density of coal than does rock dust. lt is thought that the laminarform causes the finely divided shell material to be in the form of platelets and that the relatively large surface area relative to the volume helps to carry the material in a moving airstream with float coal. ln a'preferred form thebi'valve shells are those of oysters taken from the Gulf of Mexico. An analysis of the shell material (when properly washed) shows that it is substantially all'calcium carbonate and'contains only small amounts of silica," less than 1 percent. Reduction by air impact milling followed by air classification has been particularly useful in obtaining a suitable shell material without substantial amounts of an excessively fine fraction. Explosion tests indicate that the quantity of shell material required to inhibit explosions is less than the amount of rock dust required.

While I have described a present preferred embodiment of myinvention, it is to be understood that the invention may be otherwise variously practiced within the scope of the following claims; 4

- I claim:

, l. The method of treating coal mines and the like to inhibit explosions therein which comprises introducing finely divided bivalve shell materialinto a mine and broadcasting said shell material within the mine.

Z. The method of claim 1 in which broadcasting of the finely divided shell material intermixes the shell material with finely divided carboniferous material in sufficient amount to prevent propagation: of an explosion in the finely divided carboniferous material. I

3. The method of vclaim 2 in which a major fraction of the finely divided shell material is minus 200 mesh in size.

4. The method of treating coal mines and the like to inhibit explosions therein which comprises the steps of:

a. collecting the shells of bivalves;

b. washing the shells to remove foreign material shells;

c. reducing thebivalve shells to finely divided form,

d. broadcasting the finely within the mine.

from the 5. The method of claim 4,in which broadcasting of the finely divided shell material intermixes the shell material with'finely divided carboniferous material'in sufficient amountto prevent propagation of an explosion in the finely divided carboniferous material.

6. The method of claim in which a major fractionof the finely divided shell material is minus 200 mesh in size,

'7. The method of treating coal mines and the like to inhibit explosions therein which comprises the steps of: Y

a. collecting the shells of bivalves;

b. washing the shells to remove foreign material from the shells; I c. reducingthe shells pact pulveriler; x d. classifying the size of the finely divided particles in an air f classifier; e. broadcasting the finelydivided bivalve shell material in the mine into a moving airstream and onto the walls.

to a finely divided form in an air imdivided bivalve shell material 

1. The method of treating coal mines and the like to inhibit explosions therein which comprises introducing finely divided bivalve shell material into a mine and broadcasting said shell material within the mine.
 2. The method of claim 1 in which broadcasting of the finely divided shell material intermixes the shell material with finely divided carboniferous material in sufficient amount to prevent propagation of an explosion in the finely divided carboniferous material.
 3. The method of claim 2 in which a major fraction of the finely divided shell material is minus 200 mesh in size.
 4. The method of treating coal mines and the like to inhibit explosions therein which comprises the steps of: a. collecting the shells of bivalves; b. washing the shells to remove foreign material from the shells; c. reducing the bivalve shells to finely divided form; d. broadcasting the finely divided bivalve shell material within the mine.
 5. The method of claim 4 in which broadcasting of the finely divided shell material intermixes the shell material with finely divided carboniferous material in suffIcient amount to prevent propagation of an explosion in the finely divided carboniferous material.
 6. The method of claim 4 in which a major fraction of the finely divided shell material is minus 200 mesh in size.
 7. The method of treating coal mines and the like to inhibit explosions therein which comprises the steps of: a. collecting the shells of bivalves; b. washing the shells to remove foreign material from the shells; c. reducing the shells to a finely divided form in an air impact pulverizer; d. classifying the size of the finely divided particles in an air classifier; e. broadcasting the finely divided bivalve shell material in the mine into a moving airstream and onto the walls. 